Co-existence of two different types of soluble histone complexes in nuclei of Xenopus laevis oocytes.

Kleinschmidt, Jürgen A.; Fortkamp, E.; Krohne, Georg; Zentgraf, Hanswalter; Franke, Werner W.

doi:10.1016/s0021-9258(20)71223-8

Cited by 193 publications

(39 citation statements)

References 61 publications

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“…These are depicted in figure 8. Kleinschmidt et al (1984) were able to demonstrate the coexistence of two classes of histone storage complex in Xenopus oocytes: (1) histones H3 and H4 bound to Nl and N2 and (2) histones H2a and H2b bound to nucleoplasmin, with two other histone-like bands that are also bound to nucleoplasmin. The identity of these other two proteins remains to be determined.…”

Section: N Ucleosome Assembly In Cell-free Systems From X Enopus Eggsmentioning

confidence: 97%

“…First, it fails to assemble the full complement of nucleosomes on to DNA and second, it requires very sharp optimum ratios of histones, nucleoplasmin and DNA. These shortcomings suggested that additional factors might be involved and Kleinschmidt et al (1984) have now shown that additional acidic proteins are involved in binding histones H3 and H4. These proteins are called N1 and N2; they were discovered by Bonner (1975) by their ability to enter the nucleus rapidly after injection into the cytoplasm, a property they share with nucleoplasmin.…”

Section: N Ucleosome Assembly In Cell-free Systems From X Enopus Eggsmentioning

confidence: 99%

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Chromosome replication in cell-free systems from Xenopus eggs

Blow

Dilworth

Dingwall

et al. 1987

Phil. Trans. R. Soc. Lond. B

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Cell-free systems from eggs of the frog Xenopus laevis are able to perform most of the acts of eukaryotic chromosome replication in vitro . This now includes the crucial regulatory step of initiation, which had only been achieved for viral systems previously. Purified DNA or nuclei are able to initiate and complete semiconservation replication in egg extracts in vitro (Blow & Laskey, Cell 47, 557-587 (1986)). Replication does not require specialized DNA sequences either in vitro or in microinjected eggs, but in both systems large templates replicate more efficiently than small templates. In some cases replication can re-initiate, excluding the possibility that replication is primed by preexisting primers in the template preparations. When nuclei are replicated in vitro , only one round of replication is observed in a single incubation resembling the single round of replication observed for purified DNA after micro-injection. The mechanism that prevents re-initiation of replication within a single cell cycle is discussed and certain models are eliminated. Nucleosome assembly from histones and DNA has also been studied in cell-free systems from Xenopus eggs. Fractionation has led to the identification of two acidic proteins called nucleoplasmin and N1, which bind histones and transfer them to DNA. The sequences of both proteins have been determined by cDNA cloning and sequencing. Both proteins are found as complexes with histones in eggs.

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Section: N Ucleosome Assembly In Cell-free Systems From X Enopus Eggsmentioning

confidence: 97%

Section: N Ucleosome Assembly In Cell-free Systems From X Enopus Eggsmentioning

confidence: 99%

Chromosome replication in cell-free systems from Xenopus eggs

Blow

Dilworth

Dingwall

et al. 1987

Phil. Trans. R. Soc. Lond. B

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“…The founding member of the NASP family is Xenopus laevis N1/N2, which is expressed in oocytes and specifically binds histones H3/H4, providing a mechanism for the storage of the soluble histones required for DNA replication in the early embryo [3,4]. NASP is the mammalian homolog of N1/N2 and was first described in rabbit testes as a highly autoantigenic protein which shares greater than 50% similarity to N1/N2 [5,6].…”

Section: Introductionmentioning

confidence: 99%

Molecular evolution of NASP and conserved histone H3/H4 transport pathway

Nabeel‐Shah¹,

Ashraf²,

Pearlman³

et al. 2022

Preprint

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Background: NASP is an essential protein in mammals that functions in histone transport pathways and maintenance of a soluble reservoir of histones H3/H4. NASP has been studied exclusively in Opisthokonta lineages where some functional diversity has been reported. In humans, growing evidence implicates NASP miss-regulation in the development of a variety of cancers. Although a comprehensive phylogenetic analysis is lacking, NASP-family proteins that possess four TPR motifs are thought to be widely distributed across eukaryotes. Results: We characterize the molecular evolution of NASP by systematically identifying putative NASP orthologs across diverse eukaryotic lineages ranging from excavata to those of the crown group. We detect extensive silent divergence at the nucleotide level suggesting the presence of strong purifying selection acting at the protein level. We also observe a selection bias for high frequencies of acidic residues which we hypothesize is a consequence of their critical function(s), further indicating the role of functional constraints operating on NASP evolution. Our data indicate that TPR1 and TPR4 constitute the most rapidly evolving functional units of NASP and may account for the functional diversity observed among well characterized family members. We also show that NASP paralogs in ray-finned fish have different genomic environments with clear differences in their GC content and have undergone significant changes at the protein level suggesting functional diversification. Conclusion: We draw four main conclusions from this study. First, wide distribution of NASP throughout eukaryotes suggests that it was likely present in the last eukaryotic common ancestor (LECA) possibly as an important innovation in the transport of H3/H4. Second, strong purifying selection operating at the protein level has influenced the nucleotide composition of NASP genes. Further, we show that selection has acted to maintain a high frequency of functionally relevant acidic amino acids in the region that interrupts TPR2. Third, functional diversity reported among several well characterized NASP family members can be explained in terms of quickly evolving TPR1 and TPR4 motifs. Fourth, NASP fish specific paralogs have significantly diverged at the protein level with NASP2 acquiring a NNR domain.

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“…NASP-1 forms transcriptional repressor complex with histone deacetylase HDA-1 and zinc finger-containing protein Tra4 to repress male-specific genes expression and promote female development in Caenorhabditis elegans hermaphrodites [ 17 ]. In Xenopus laevis , N1/N2 allows the progressive release of histones after fertilization and thus ensures nucleosomal assembly during rapid cell divisions in early development [ 18 , 19 ]. Reducing mammalian NASP in tissue culture cells results in a defect in cell proliferation.…”

Section: Introductionmentioning

confidence: 99%

The histone chaperone Nrp1 is required for chromatin stability and nuclear division in Tetrahymena thermophila

Lian

Hao

et al. 2021

Epigenetics & Chromatin

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Histone chaperones facilitate DNA replication and repair by promoting chromatin assembly, disassembly and histone exchange. Following histones synthesis and nucleosome assembly, the histones undergo posttranslational modification by different enzymes and are deposited onto chromatins by various histone chaperones. In Tetrahymena thermophila, histones from macronucleus (MAC) and micronucleus (MIC) have been comprehensively investigated, but the function of histone chaperones remains unclear. Histone chaperone Nrp1 in Tetrahymena contains four conserved tetratricopepeptide repeat (TPR) domains and one C-terminal nuclear localization signal. TPR2 is typically interrupted by a large acidic motif. Immunofluorescence staining showed that Nrp1 is located in the MAC and MICs, but disappeared in the apoptotic parental MAC and the degraded MICs during the conjugation stage. Nrp1 was also colocalized with α-tubulin around the spindle structure. NRP1 knockdown inhibited cellular proliferation and led to the loss of chromosome, abnormal macronuclear amitosis, and disorganized micronuclear mitosis during the vegetative growth stage. During sexual developmental stage, the gametic nuclei failed to be selected and abnormally degraded in NRP1 knockdown mutants. Affinity purification combined with mass spectrometry analysis indicated that Nrp1 is co-purified with core histones, heat shock proteins, histone chaperones, and DNA damage repair proteins. The physical direct interaction of Nrp1 and Asf1 was also confirmed by pull-down analysis in vitro. The results show that histone chaperone Nrp1 is involved in micronuclear mitosis and macronuclear amitosis in the vegetative growth stage and maintains gametic nuclei formation during the sexual developmental stage. Nrp1 is required for chromatin stability and nuclear division in Tetrahymena thermophila.

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Co-existence of two different types of soluble histone complexes in nuclei of Xenopus laevis oocytes.

Cited by 193 publications

References 61 publications

Chromosome replication in cell-free systems from Xenopus eggs

Chromosome replication in cell-free systems from Xenopus eggs

Molecular evolution of NASP and conserved histone H3/H4 transport pathway

The histone chaperone Nrp1 is required for chromatin stability and nuclear division in Tetrahymena thermophila

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